Canned motor pump and method for manufacturing such a motor pump

ABSTRACT

The invention relates to a canned motor pump (P1) comprising: a housing (10) including a body (11) and a motor casing (12); an electric motor (20) including a stator (30) and a rotor (40) arranged in the motor casing (12); a shaft (50), extending along a central axis (X1), secured with the rotor (40) to rotate therewith about the central axis (X1), and having a front end (52) located outside the motor casing (12), in the body (11) of the housing (10); and a wheel (60) located at the front end (52) of the shaft (50), secured with the shaft (50) to rotate therewith about the central axis (X1) and having a hydraulic profile suitable for moving a fluid (F) in the body (11). The rotor (40), the shaft (50) and the wheel (60) form a rotary assembly (ER1). Within the rotary assembly (ER1), only the shaft (50) is supported by one or more bearings (80), thereby guiding the rotary assembly (ER1) in rotation. The motor pump (P1) is characterized in that the shaft (50) and the wheel (60) form, at least partially, a single-piece part (70). A method for manufacturing such a motor pump (P1) is also described.

The present invention relates to a canned motor pump. More particularly, the invention relates to a method for manufacturing such a motor pump.

By definition, a canned motor pump comprises both a pump and a motor, arranged within a hermetically sealed housing. The motor pump comprises a fluid inlet opening and outlet opening. When the motor pump is integrated into an industrial installation, sealing is also ensured at the inlet and outlet openings.

Various constructions of canned motor pumps are known, for example the documents EP2607709A1, JP2007127135A, U.S. Pat. No. 6,010,319A and WO200123763A1.

These motor pumps comprise a housing, an electric motor, a central shaft and a wheel. The housing comprises a motor casing. The electric motor comprises a stator and a rotor arranged within the motor casing. The shaft, the rotor and the wheel form a rotary assembly. The central shaft is supported by two main bearings. The wheel is attached to the front end of the shaft situated outside the motor casing.

In U.S. Pat. No. 6,010,319A, the shaft and the wheel are very distinct. The sleeve formed at the central part of the wheel simply constitutes a part of this wheel, intended for the mounting thereof upon the shaft. The sleeve does not guide the rotary assembly in rotation. In this case, the sleeve of the wheel constitutes a means of attachment by binding the wheel onto the shaft, but cannot be regarded as constituting a part of the shaft, being incapable of guiding the shaft specifically in rotation. Furthermore, it is possible to change the wheel independently of the shaft.

The objective of the present invention is to propose an improved motor pump.

To this end, the purpose of the invention is a canned motor pump comprising: a housing including a body and a motor casing; an electric motor including a stator and a rotor arranged within the motor casing; a shaft which extends along a central axis, which is secured to the rotor in rotation about the central axis, and which has a front end located outside the motor casing, within the body of the housing; and a wheel which is located at the front end of the shaft, which is secured to the shaft in rotation about the central axis, and which has a hydraulic profile suitable for moving a fluid in the body. The rotor, the shaft and the wheel form a rotary assembly. Within the rotary assembly, only the shaft is supported by one or more bearings, thereby guiding the rotary assembly in rotation. The motor pump is characterized in that the shaft and the wheel constitute at least partially a unitary part.

Thus, the motor pump according to the invention offers many advantages. By virtue of the canned rotor, the motor pump has absolute tightness, high reliability, and low maintenance. The unitary part formed by the shaft and the wheel may be manufactured using various techniques, including additive fabrication of the part or the mold wherein this piece is molded. This provides responsiveness and freedom for the design of geometric shapes in order to improve the efficiency of the motor pump. In particular, a greater freedom of design is offered at the central part of the wheel. This also makes it possible to improve the NPSH characterizing the suction performance of the motor pump. Combined with a synchronous motor, shorter and maintaining the very high energy efficiency thereof with a large air gap, the design is simplified in being more compact and with fewer components. The large air gap makes it possible to consider new sealing solutions for the stator, improving the efficiency of the motor and therefore of the motor pump.

Furthermore, the motor pump according to the invention has great versatility. This motor pump can be implemented within numerous, industrial or domestic applications in: agri-food, chemicals, pharmaceuticals, oil, phosphoric fertilizers, metallurgy, marine, boiler, desalination, evaporation, etc.

According to other advantageous characteristics of the motor pump according to the invention, taken alone or in combination:

-   -   The shaft and the wheel integrally constitute a single unitary         part.     -   The wheel comprises a central portion, which is located on the         central axis, belongs to the unitary part, and has no attachment         system.     -   The central part forms an inducer.     -   The central portion includes an extension to the blades of the         wheel.     -   The motor pump comprises a single bearing supporting the shaft         radially to the central axis in order to guide the rotary         assembly in rotation, and which is located between the rotor and         the wheel along the central axis.     -   The motor pump comprises a front bearing and a rear bearing         supporting the shaft radially to the central axis for guiding         the rotary assembly in rotation, the front bearing being located         between the rotor and the wheel along the central axis.     -   The electric motor is constructed according to synchronous motor         technology with magnets at the rotor.     -   The stator, comprising an electromagnetic core and a winding,         has an inner surface entirely enveloped in a non-metallic         material, facing the rotor and in contact with the fluid         circulating within the motor casing.     -   The stator is embedded within a sealed resin coating, at least         along the inner surface.     -   The motor pump is a centrifugal pump, the hydraulic profile of         the wheel being suitable for the transmission of energy by the         centrifugation of fluid.

The subject of the invention is also a method for manufacturing a motor pump as described above. According to this method, the shaft and the wheel are at least partially manufactured as a unitary part, for example according to a technique of sand, metal mold or lost wax casting, sintering, welding, additive fabrication, or a combination of several techniques.

According to a first specific embodiment, the method comprises an additive fabrication operation of the unitary part.

According to a second specific embodiment, the method comprises an additive fabrication operation of at least a portion of a mold comprising a cavity corresponding to the unitary part, and then a fabrication operation for the unitary part within this mold. The additive fabrication operation may consist of the manufacture of the mold in the entirety thereof, or only a part of this mold, in particular at the junction between the shaft and the wheel.

Preferably, the shaft and the wheel are integrally manufactured as a unitary part.

The method may also include other operations within the scope of the invention. For example, the method may include machining operations, heat treatment, coating, etc.

The invention will be better understood upon reading the following description, given solely as a non-limiting example, and made with reference to the accompanying figures wherein:

FIG. 1 is a longitudinal sectional view of a motor pump according to the state of the art;

FIG. 2 is a larger scale view of the detail II in FIG. 1;

FIG. 3 is a longitudinal sectional view similar to FIG. 1, showing a motor pump according to a first embodiment of the invention;

FIG. 4 is a larger scale view of the detail IV in FIG. 3;

FIG. 5 is a longitudinal sectional view analogous to FIG. 1, showing a motor pump according to a second embodiment of the invention; and

FIG. 6 is a longitudinal sectional view similar to FIG. 1, showing a shaft variant designed to equip a motor pump according to the invention.

In FIGS. 1 and 2 an example is shown of a canned centrifugal motor pump P0 that is known from the state of the art.

The motor pump P0 comprises a housing 1, an electric motor 2, a shaft 5, a wheel 6, a screw 7 and bearings 8 and 9. The electric motor 2 comprises a stator 3 and a rotor 4 centered on a central axis X1. The rotor 4 is secured with the shaft 5, itself secured with the wheel 6. The screw 7 makes it possible to secure the wheel 6 at the end of the shaft 5. The rotor 4, the shaft 5 and the wheel 6 form a rotary assembly, rotatable about the central axis X1.

The housing 1 is partially shown with the aim of simplification. The housing 1 includes a body 1 a partially represented by dotted lines, a motor casing 1 b and a cover 1 c. The stator 3 and the rotor 4 are arranged within the motor casing 1 b. The cover 1 c closes the motor casing 1 b at the rear bearing 9.

The stator 3 comprises an electromagnetic core 3 a, a winding 3 b, a resin coating 3 c and a metal liner 3 d. The winding 3 b extends on either side of the core 3 a according to the axis X1 and is embedded within the coating 3 c. The liner 3 d extends along the stator 3, at the air gap formed with the rotor 4, in order to ensure the sealing of the stator 3. The liner 3 d is in contact both with the core 3 a and the coating 3 c. This configuration is a source of losses due to eddy currents within the liner 3 d.

A canned centrifugal motor pump P1 according to a first embodiment of the invention is shown in FIGS. 3 and 4.

The motor pump P1 comprises a housing 10, an electric motor 20 comprising a stator 30 and a rotor 40, a shaft 50, a wheel 60 and a bearing 80. The electric motor 20 comprises a stator 30 and a rotor 40 centered on a central axis X1. The rotor 40 is secured with the shaft 50, itself secured with the wheel 60, as detailed below.

The housing 10 includes a body 11 arranged on the front side and a motor casing 12 arranged on the rear side of the motor pump P1. The body 11 is partially shown by a dotted line for the purpose of simplification. The casing 12 comprises various walls 14, 15, 16 and 18 secured to one another. The outer wall 14 has a cylindrical profile. The front wall 15 has a flat annular shape, surrounding the wall 18. The rear wall 16 has a planar disc shape. The front wall 18 has a cylindrical shape and constitutes a bearing support.

The stator 30 comprises an electromagnetic core 31 and a winding 32, which extends on either side of the core 31 along the axis X1. The core 31 and the winding 32 are embedded within a resin encapsulation 33, thereby sealing the stator 3. The encapsulation 33 extends all along the stator 30, at the air gap formed with the rotor 40. The stator 30 has no metallic liner. By virtue of the use of an encapsulation 33 in place of the metallic liner of the stator 30, the eddy current losses are eliminated.

According to the invention, the shaft 50 and the wheel 60 constitute at least partly a unitary part 70. In other words, the part 70 comprises at least a portion of the shaft 50 and at least a portion of the wheel 60. One or more other portions of the shaft 50 and/or the wheel 60 may be formed by one or more different parts of the part 70.

According to a preferred embodiment, shown in the figures, the shaft 50 and the wheel 60 entirely constitute a single unitary part 70. In other words, the part 70 embodies the entire shaft 50 and the wheel 60. They are not formed by anything other than the part 70.

By way of non-limiting examples, the part 70 may be manufactured according to various techniques of sand, metal mold or lost wax casting, sintering, welding, additive fabrication of the part 70, additive fabrication of the mold, or a combination of several techniques.

Advantageously, the part 70 can be manufactured entirely by means of additive fabrication. According to an equally advantageous alternative, the part 70 can be cast in a mold, itself obtained at least in part by means of additive fabrication.

The rotor 40 and the part 70 form a rotary assembly ER1, rotatable about the axis X1, within the motor pump P1.

The shaft 50 extends along the axis X1, with a main portion 51 connecting a front end 52 and a rear end 53. The rotor 40 is secured with the shaft 50 at the main portion 51 thereof, by any known means. The main portion 51 and the rear end 53 are located within the motor casing 12. The front end 52 is located outside the motor casing 12, within the body 11 of the casing 10.

The wheel 60 comprises a central portion 61, blades 62, an inlet opening 63, inner channels 64 and outlet openings 65. The wheel 60 is located outside the motor casing 12, within the body 11 of the housing 10. The wheel 60 has a hydraulic profile suitable for moving a fluid F within the body 11. More precisely the motor pump P1 is a centrifugal pump, that is to say the hydraulic profile of the wheel 60 is suitable for the transmission of energy by the centrifugation of fluid F within the motor pump P1. The fluid F enters the opening 63, then passes through the channels 64 arranged within the wheel 60, to the outlet orifices 65.

The central portion 61 is located on the axis X1 and is secured with the front end 52 of the shaft 50. Insofar as the shaft 50 and the wheel 60 constitute the part 70, the central portion 61 can have no fastening system, for example of the screw type 7, provided for in the state of the art. This offers greater design freedom near this central part 61.

In the example of FIG. 3, the central portion 61 has a concave shape, formed projecting from the front side, in such a way as to guide the fluid F entering the opening 63 and then the channels 64.

Alternatively, the central portion 61 may be shaped as an inducer. According to another alternative, the central portion 61 may include an extension to the blades 62 of the wheel 60. These two alternatives can be combined.

Within the rotary assembly ER1, only the shaft 50 is supported by the bearing 80. In other words, only the shaft 50, together with the bearing 80, guides the rotary assembly ER1 in rotation.

The bearing 80 is located between the rotor 40 and the wheel 60, along the axis X1. The bearing 80 can therefore be described as a center bearing, in relation to the rotary assembly ER1. The bearing 80 comprises the wall 18 and two members 81 and 82, which are accommodated within the bore defined by the wall 18. The elements 81 and 82 are spaced slightly apart, and support the main portion 51 of the shaft 50 radially to the axis X1. The elements 81 and 82 are, for example, plain bearings or rollers.

This design with a central bearing 80 is made possible by means of the use of a motor 20 with a relatively short length along the axis X1. Thus, the rotor 40 may be cantilevered from the side of the rear end 53 of the shaft 50. This solution is allowed by the use of the technology of the synchronous motor with magnets on the rotor 40. Such a motor offers optimum performance over the entire speed range as well as reduced weight and bulk.

In FIG. 5 a canned centrifugal motor pump P2 according to a second embodiment of the invention is shown. Some constituent elements of the motor pump P2 are comparable to those of the motor pump P1 described above and, for purposes of simplification, bear the same numerical references.

The motor pump P2 comprises two bearings 8 and 9 arranged on either side of the rotor 40. The bearing 8 supports the main portion 51 of the shaft 50 between the rotor 40 and the wheel 60, while the bearing 9 supports the rear end 53 of the shaft 50. Each bearing 8 and 9 comprises a single element, respectively 81 and 91, supporting the shaft 50. For example, the elements 81 and 91 may be plain bearings or rollers. Each bearing 8 and 9 comprises a cylindrical wall, 18 and 19 respectively, of the housing 10. Each of the elements 81 and 91 is mounted within the bore defined by one of the walls 18 and 19. The housing 10 comprises a cover 13 for closing the casing 12 at the bearing 9.

FIG. 6 shows a variant of the wheel 60, designed to equip a pump P1 or P2 according to the invention.

The central portion 61 of the wheel 60 is shaped as an inducer, provided in order to improve the capacity for suction of the fluid F by the wheel 60.

In addition, the central portion 61 includes an extension to the blades 62 of the wheel 60, also making it possible to improve the capacity for suction of the fluid F by means of the wheel 60.

In practice, the motor pump P1/P2 can be configured differently from FIGS. 3 to 6 without going beyond the scope of the invention. Moreover, the technical characteristics of the various embodiments and variants mentioned above can, in whole or for some thereof, be combined with one another. Thus, the pump P1/P2 may be adapted in terms of cost, functionality and performance. 

1. Canned motor pump (P1; P2) comprising: a housing (10) comprising a body (11) and a motor casing (12); an electric motor (20) comprising a stator (30) and a rotor (40) arranged within the motor casing (12); a shaft (50) which extends along a central axis (X1), which is secured to the rotor (40) in rotation about the central axis (X1), and which has a front end (52) situated outside the motor casing (12), within the body (11) of the housing (10); and a wheel (60) which is located at the front end (52) of the shaft (50), which is secured to the shaft (50) in rotation about the central axis (X1), and which has a hydraulic profile suitable for moving a fluid (F) within the body (11); the rotor (40), the shaft (50) and the wheel (60) forming a rotary assembly (ER1; ER2); and within the rotary assembly (ER1, ER2), only the shaft (50) is supported by one or more bearings (80; 8, 9), thus guiding the rotary assembly (ER1, ER2) in rotation; wherein the shaft (50) and the wheel (60) constitute at least partly a unitary part (70).
 2. Canned motor pump (P1; P2) according to claim 1, wherein the shaft (50) and the wheel (60) integrally constitute a single unitary part (70).
 3. Canned motor pump (P1; P2) according to claim 1, wherein the wheel (60) comprises a central portion (61), which is located on the central axis (X1), belongs to the unitary part (70), and has no attachment system.
 4. Canned motor pump (P1; P2) according to claim 3, wherein the central part (61) forms an inducer.
 5. Canned motor pump (P1; P2) according to claim 3, wherein the central portion (61) includes an extension to the blades (62) of the wheel (60).
 6. Canned motor pump (P1) according to claim 1, wherein the canned motor pump (P1) comprises a single bearing (80) supporting the shaft (50) radially to the central axis (X1) for guide the rotary assembly (ER1) in rotation, and which is located between the rotor (40) and the wheel (60) along the central axis (X1).
 7. Canned motor pump (P2) according to claim 1, wherein the canned motor pump (P2) comprises a front bearing (8) and a rear bearing (9) supporting the shaft (50) radially to the central axis (X1) for guiding the rotary assembly (ER2) in rotation, the front bearing (8) being located between the rotor (40) and the wheel (60) along the central axis (X1).
 8. Canned motor pump (P1; P2) according to claim 1, wherein the electric motor (20) is constructed according to synchronous motor technology with magnets at the rotor (40).
 9. Canned motor pump (P1; P2) according to claim 1, wherein the stator (30), comprising an electromagnetic core (31) and a winding (32) has an inner surface entirely enveloped in a non-metallic material, facing the rotor (40) and in contact with the fluid (F) circulating within the motor casing (12).
 10. Canned motor pump (P1; P2) according to claim 9, wherein the stator (30) is embedded in a sealed resin coating (33), at least along the inner surface.
 11. Canned motor pump (P1; P2) according to claim 1, wherein the canned motor pump (P1; P2) is a centrifugal pump, the hydraulic profile of the wheel (60) being suitable for the transmission of energy by the centrifugation of fluid (F).
 12. A method for manufacturing a canned motor pump (P1; P2) according to claim 1, wherein the shaft (50) and the wheel (60) are at least partially manufactured in the form of a unitary part (70), according to a technique of sand casting, metal mold casting or lost wax casting, sintering, welding, additive fabrication, or a combination of several techniques.
 13. A method for manufacturing a canned motor pump (P1; P2) according to claim 12, wherein the method comprises an operation of additive fabrication of the unitary part (70).
 14. A method of manufacturing a canned motor pump (P1; P2) according to claim 12, wherein the method comprises an operation of additive fabrication of at least a portion of a mold comprising a cavity corresponding to the unitary part (70), and then an operation of fabrication of the unitary part (70) within this mold. 